The use of intravascular guidewires, catheters and other types of elongate delivery members for accessing and treating various types of vascular disease is well-known. In general, a suitable intravascular guidewire, catheter or other delivery member inserted into the vascular system, e.g., via introduction through a femoral or jugular artery or vein, and navigated through the vasculature to a desired target site. By using an appropriately sized device having the requisite performance characteristics, such as “pushability” “steerability”, “torquability” and most important, distal tip flexibility, virtually any target site in the vascular system may be accessed, including within the tortuous cerebral vasculature.
For example, balloon catheters are used in a number of endovascular applications, including for temporarily or permanently occluding blood flow either distal or proximal of a treatment site during neurological examinations, delivering diagnostic agents such as contrast media, assisting in neurovascular embolic coiling of an aneurysm or arteriovenous malformation (AVM), and dilating narrowed blood vessels caused by vasospasm. During therapeutic procedures such as the ones mentioned above, the distal ends of some balloon catheters are substantially sealed by a guidewire inserted into the catheter lumen for inflation of a balloon portion by pressurized inflation fluid. To facilitate a more complete and secure seal of the balloon portion against the distal end of the guidewire, the guidewire is preferably configured such that its outer diameter is substantially constant along its longitudinal axis. As used in this application, a “substantially constant” elongate member outer diameter is an outer diameter that varies less than about 20% from the average outer diameter along the elongate member's longitudinal axis.
Many medical devices, such as guidewires, incorporate slots into their construction. Incorporating slots into medical devices can modify or customize the device flexibility/stiffness, especially of elongate medical devices. Examples of slotted medical devices are described in U.S. Pat. No. 5,095,915, the entire disclosure of which is incorporated herein by reference, as though set forth in full.
More specifically, guidewires may include slotted metallic hypotubes. Such slotted hypotubes provide superior performance characteristics (i.e., pushability, steerability, torquability, and flexibility/stiffness) for accessing cerebral blood vessels. Further, slot patterns in guidewire tubular shafts can be varied to modify or customize the stiffness of various portions of guidewires. For instance, distal portions of guidewire shafts may have a slot pattern (e.g., more slots per area, longer slots, and/or wider slots) that decreases the stiffness thereof. When used as components of guidewires, the slotted hypotubes are preferably substantially sealed to prevent inflation fluids from entering into the inner lumen of the tube, and also to enhance lubricity. Exemplary slotted hypotubes are disclosed and described in U.S. Pat. Nos. 8,858,643 and 9,162,040, the entire disclosures of which are incorporated herein by reference, as though set forth in full.
Many medical devices are also coated to improve their functionality. For instance, some medical devices are coated with a lubricious polymer to reduce friction when the devices are inserted into catheters and body lumens. Coating slotted medical devices can also close the slots therein, render at least portions of the slotted medical devices fluid-tight. Examples of coated medical devices are described in U.S. Pat. Nos. 5,443,455 and 6,488,637, the entire disclosures of which are incorporated herein by reference, as though set forth in full.
Medical devices are coated using various methods, such as spray coating, dip coating, extrusion and lamination. Regardless of the coating method, variations in the slot volume (i.e., the total volume of slots formed in a longitudinal section per section length) of different regions of the slotted tube can result in different outer diameters in these regions, because the slots function as reservoirs or sinks for receiving a liquid coating material. Accordingly, varying slot patterns to modify the stiffness of various regions of guidewires may change the slot volume of those regions, and inadvertently vary the outer diameter of those regions. This can result in undesired effects, such as failure to substantially seal the distal ends of some balloon catheters and corresponding inflation fluid leakage and reduced balloon performance.